For each of the following situations, draw

a diagram, and write the differential

energy balance equation, eliminating any

terms that are zero or negligible. State

whether the system is open or closed.

Also state whether any heat or work is

positive or negative.

(a) Crude oil is pumped through a

cross-country pipeline. The pipe

inlet is 200 m higher than the outlet,

the pipe diameter is constant, and

the pump is located near the mid-

point of the pipeline. The entire

pipeline is insulated. System: pipe-

line and its contents.

(b) Nitrogen and hydrogen are fed at a

constant rate to a reactor operating

at steady state, where they react to

ammonia. The inlet and outlets have

the same diameter and the same

height above the ground. System:

reactor and its contents.

(c) Milk is pumped continuously

through the inner pipe of a double-

pipe heat exchanger, where it is

heated from 25°C to 80°C. System:

the inner pipe and its contents.